Peroxycarboxylic acid compositions can be effective antimicrobial agents. Methods of using peroxycarboxylic acids to clean, disinfect, and/or sanitize hard surfaces, textiles, meat products, living plant tissues, and medical devices against undesirable microbial growth have been described (U.S. Pat. Nos. 6,545,047; 6,183,807; 6,518,307; U.S. Patent Application Publication No. 2003-0026846; and U.S. Pat. No. 5,683,724). Peroxycarboxylic acids have also been used in various bleaching applications including, but not limited to, wood pulp bleaching/delignification and laundry care applications (European Patent 1040222B1; U.S. Pat. Nos. 5,552,018; 3,974,082; 5,296,161; and 5,364,554). The desired efficacious concentration of peroxycarboxylic acid may vary according to the product application (for example, ca. 500 ppm to 1000 ppm for medical instrument disinfection, ca. 30 ppm to 80 ppm for laundry bleaching or disinfection applications) in 1 min to 5 min reaction time at neutral pH.
Enzymes structurally classified as members of family 7 of the carbohydrate esterases (CE-7) have been employed as perhydrolases to catalyze the reaction of hydrogen peroxide (or alternative peroxide reagent) with alkyl esters of carboxylic acids in water at a basic to acidic pH range (from ca. pH 11.5 to ca. pH 5) to produce an efficacious concentration of a peroxycarboxylic acid for such applications as disinfection (such as medical instruments, hard surfaces, textiles), bleaching (such as wood pulp or paper pulp processing/delignification, textile bleaching and laundry care applications), and other laundry care applications such as destaining, deodorizing, and sanitization (U.S. Pat. Nos. 7,964,378; 7,951,566; and 7,723,083 and Published U.S. Patent Application Nos. 2008-0176299, and 2010-0041752 to DiCosimo et al.). The CE-7 enzymes have been found to have high specific activity for perhydrolysis of esters, particularly acetyl esters of alcohols, diols, glycerols and phenols, and acetyl esters of mono-, di- and polysaccharides.
Published U.S. Patent Application No. 2010-0087529 to DiCosimo et al. describes several variant CE-7 perhydrolases derived from several Thermotoga sp. having higher perhydrolytic specific activity and/or improved selectivity for perhydrolysis when used to prepare peroxycarboxylic acid from carboxylic acid esters. Two of the variants described in Published U.S. Patent Application No. 2010-0087529, Thermotoga maritima C277S and Thermotoga maritima C277T, exhibited a significant improvement in specific activity relative to the T. maritima wild-type enzyme.
Thermotoga maritima variants having higher peracid stability were also reported by DiCosimo et al. in U.S. Pat. Nos. 7,927,854; 7,923,233; 7,932,072; 7,910,347, and 7,960,528. Each variant was characterized as having an increased peracetic acid formation to peracetic acid hydrolysis ratio (PAAF:PAAH) when compared to the T. maritima wild-type perhydrolase or the T. maritima C277S variant perhydrolase.
Several variants of the Thermotoga maritima C277S perhydrolase have been identified which have higher specific activity for the perhydrolysis of esters when compared to the specific activity of the Thermotoga maritima C277S (U.S. Patent Application Nos. 2011-0236335, 2011-0236336, 2011-0236337, 2011-0236338, and 2011-0236339 to DiCosimo et al.). However, there remains a need to identify additional variants having an increase in perhydrolytic specific activity.
The problem to be solved is to provide an enzyme catalyst comprising a CE-7 perhydrolase having higher specific activity for the perhydrolysis of esters when compared to the specific activity of the Thermotoga maritima C277T perhydrolase.